Now, Facebook has added a new Mobile Recharge option in the Settings menu. This option does the exact same thing which it says in the title, it helps you to top up your prepaid smartphone. It supports all the major networks in India and it lists all the voice and data plans to choose from while recharging.
Steps to recharge mobile using Facebook App
The Facebook app only supports debit and credit card payment methods so you got to have one ready. Facebook might add more payment methods like UPI and wallet payments in the future but we cannot say for sure right now.